Speed control apparatus



April 29, 1941- s. T. WEBSTER 2,240,322

SPEED CONTROL APPARATUS l Filed Aug. 24, 1939 L Patented Apr. ze, 1941 fcirco sr T i ortica Claims.

This invention relates' to the control of speed in a plurality ofelectric or hydraulic motors or other motor units.

It is the general object of my invention to pror vide apparatus by whichthe speed of each motor unit may be separately regulated, and by whichalso the speeds of all ofthe motor units may be increased or decreasedsimultaneously, while maintaining an established speed ratio between thedilierent units.

A further object of the invention is to provide apparatus tosimultaneously control the directions of rotation of different motorunits (assuming the same to be reversible), as well as controlling themotor unit speeds, and while also maintaining an established speed ratiobetween the diierent units.

To the attainment of these objects, I provide a manually adjustablecontroller for each motor unit, and a master controller for all of theunits.

A preferred form of the invention is shown in the drawing which is adiagrammatic view showing certain hydraulic motors and associatedmechanism, with my improved control apparatus applied thereto.

Referring to the drawing, I have shown two hydraulic motors lVl and M2driven by pumps P and P2 which draw liquid from tanks T' and T2 andwhich are provided with valves V and V2 by which the speed and directionof rotation of the motors may be directly controlled.

The motors are connected to theirv respective valves by pipes IU and Il,and return pipes l2 and i3 are provided, which are also connected to thepressure pipes I4 and I5 by relief valves I6 and il through which thepumps discharge any excess oil not used by the motors when the valvesare in such positions as to throttle the oil flow to the motors.

The valves V and V2 are provided with valve stems 2@ and 2l connected bylinks 22 and 23 to crank arms 4 and 25 fixed to worm gears 25 and El.and angularly movable therewith. The worm gears are moved by worms 23and 2S mounted on the armature shafts 3i! and 3l of auxiliary motors 32and 33, preferably of commutator type. Rotation of either oi thesemotors or 33 in either direction will correspondingly shift theassociated valve, thus controlling the speed direction of rotation ofthe corresponding motor M or M2.

Index pointers 36 and 35 move with the valve stems 25 and 2! andindicate the positions of the valves on suitable scales which may bearthe letters F, S and R as shown, indicating forward, stop and reverseThe auxiliary motor 32 is provided with reversely wound eld coils 4B and4l connected to terminals 42 and 43. Associated terminals 44 and 45 arejointly connected to one pole of a battery B' or other suitable sourceof power, the other pole of the battery being connected to one of thebrushes of the motor 32, with Athe other brush connected to the fieldcoils.

When the field coil 4D' is energized, the motor 52 will revolve in onedirection, and when the coil il is energized, the motor will revolve inthe opposite direction.

The motor 33 is correspondingly provided with eld coils 50 and 5l,connected to terminals 52 and 53, and having associated terminals 54 and55 connected to a battery B2 or other suitable source of power.

Contact plates 46 are mounted on a swinging arm 4T and are adapted toclose the circuit through the terminalsZ-M or the terminals i3-G5,according to therdire'ction in which the arm 4l is displaced. Springs 48normally maintain the arm 41 in mid or neutral position. The arm 4l ispart of a permanent magnet 49 having poles N and S and caused to swingin one direction or the other by electrical control means to bedescribed.

Similar plates 56 are provided for the motor 33, said plates beingsupported by an arm 5l normally centered by springs 58 and forming partof a permanent magnet 59 having poles N and S.

A control device C is provided for the armA 41, thereby determining theselected position of the valve V', and a similar control device C2 isprovided for the arm 51, thereby determining the selected position ofthe valve V2.

The control device C comprises a coil 6E] which coacts with thepermanent magnet 49 to swing the arm il to the right or left fromneutral position, according to the direction of current ow through thecoil 50. i

One end of the coil El) is connected through a wire 62 to one of thebrushes of a small commutator type generator G', the armature of whichcoacts with a permanent magnet iield system S. The generator G' iscontinuously driven in constant speed relation to the motor M', and thedirect current voltage generated by G is proportional to the speed ofmotor M. The other brush of the generator G is connected through a wire63 to a contacter S4 which is movable manually along equal resistances65 and 66 and which may make contact therewith at any point in eitherresistance. The contactor 84 thus manually determines the normal speedand direction of rotation of the motor M. At their adjacent ends, theresistances 65 and 66 are jointly connected by a wire 81 to the coil 80.

Precisely similar connections are provided in the control mechanism C2,including a contactor 18, equal resistances l'l and '12,a wire 'I3 fromthe adjacent ends of the resistances to a coil T4, and wires 7 5 and I6connecting the coil 14 and the contactor 'ID respectively with thebrushes of a commutator type generator G2, the armature of which ooactswith a permanent magnet eld system S2. The generator G2 is continuouslydriven in constant speed relation to the motor M2 and the direct currentvoltage generated by G2 is proportional to the speed of the motor M2.

I also provide a master controller C3 which comprises equal resistances80 and 8l having their adjacent ends jointly connected to a battery B3or other source of direct current. The opposite pole of the battery isconnected through a wire 82 to a contactor 83 which may be manuallymoved to engage a control resistance 8i at any desired point.

One end of the control resistance 84 is connected by a wire 85 to thefree end of the resistance 8 I and the opposite end of the resistance 84is connected by a `wire 86 to the free end of the resistance Bil.

The wire 85 is connected by a wire Sli to the free end of the resistance'H in the controller C2, and the wire 86 is connected by a Wire 9| tothe free end of the resistance 66 in the controller C. The free ends ofthe resistances 65 and T2 are connected by a wire 93.

The operation of my improved control apparatus is as follows:

Assuming that the contactor 83 of the master controller C3 is in theposition shown in full lines and that the contactor 83 is connected withone pole of the battery B3 as shown and described, there will then betwo internal and one external return circuit available from thecontactor 83 to the other pole of the battery B3, all of said circuitsbeing parallel.

One internal circuit is through the resistance 8l, a second internalcircuit is through the resistances 84 and 80 in series, and the third orexternal circuit is through the wire 90, resistances 'H and '12, wire93, resistances 65 and 66, wire 9| and resistance 80. A strictlyproportional part of the current will ow through the external circuitand through the controllers C' and C2. As the total current flow isnegligible, the Waste of current by iiowing through the internalcircuits is immaterial.

If the contactor 83 is moved toward the central point H18 of the controlresistance 85, the amount of current flowing through the externalcircuit described will be reduced as an increasing part of theresistance 84 is introduced into the external circuit.

When the contactor 83 reaches the middle point lili), the branchcircuits through the right and left halves of the resistance 84 andthrough the resistances 8i] and 8| will be balanced so that the wires 85and 85 will be at the same potential and there will be no currentflowing through the external circuit.

When the contactor 83 is moved further to the left beyond the neutralpoint 88, a current will ilow in the opposite direction in the externalcircuit Si, 85, 35, 93, 12, 'H and Sil, and since the resistance 84 iswound with uniform resistance per unit length, the current will beproportional to the distance contactor 83 is moved from point |00.

Assume that the individual controllers C and C2 are set to cause M andM2 to rotate in some definite speed ratio, and to run in certaindirections, and assume that the contactor 83 of the controller C3 is inthe extreme right-hand position shown by full lines. Then, if 33 ismoved over to the extreme left-hand position, as shown by dotted lines,both motors would come to a stop, accelerate in the opposite direction,and nally reach their original speeds.

The contactor 83 may be moved manually, as by a suitable lever or handwheel arrangement, to various points of contact with the resistance 84,or any suitable automatic means may be provided ior moving the contactor83 in accordance with any selected phenomena.

The operation of the master controller C3 on the separate primarycontrollers C and C2 is the same for both units and will now bedescribed with reference to the controller C and the motor M.

The contactor El! of the controller C is shown in the drawing as beingin mid position and as engaging the resistances and 66 at their commonpoint of attachment to the wire 61. Under these conditions, no currentwill flow through the coil 6D, the arm Ill will remain in mid position,and there will be no operation of the motor 32 to shift the valve V frommid or neutral position.

If, however, the contactor 64 is moved to the right or to the left fromthe position shown, there will then be a difference in potential betweenthe contactor S4 and the Wire 61, thus causing current to flow in onedirection or the other through the coil 60 and correspondinglydisplacing the arm 41 to close a circuit through one or the other of thefield coils 48 and 4I of the motor 32.

The motor 32 will then revolve and will turn the worm 28 to shift thevalve V to start the motor M in a desired direction. This simultaneouslystarts the generator G', which is so connected that it generates avoltage in the circuit of the controller C which is opposite inpotential to the voltage developed by movement of the contactor 64 frommid position as above described.

As the motor M increases in speed, a point will be reached Where thesetwo voltages neutralize each other, whereupon the current in coil 60 isreduced to zero and the arm 41 returns to mid position, leaving thevalve V in the position to which it has been moved by the motor 32. Themotor M thereafter continues to operate at a speed directly dependent onthe displacement of the contactor 64.

If the motor M should tend to further increase its speed, the voltagegenerated by the generator G will overbalance the voltage due to theposition of the contactor 64, and the current in coil 60 will bereversed and move the arm 41 in the opposite direction, thereby causingthe motor 32 to reversely adjust the valve V' until a balanced positionis reached.

If the displacement of the contactor E4 is to the right, the motor 32will shift the valve V in one direction, while if the displacement is tothe left, 4the valve V will be shifted in the opposite direction.

It should be noted that the controllers C and C2 are independent, sothat the contactor 64 in the controller C may be set to cause the motorM' to operate at a certain speed forward or clockwise, while thecontacter in the controller C2 may be set at such a point that the motorM2 will operate at half speed in the reverse direction. Any otherdesired combination may be selected.

In any event, movement of the contactor 83 along the resistance .84 willvary the current flowing through the external circuit of the controllerC3 and will thus vary the current which flows through the coils 6U and14, so that these currents will be neutralized at relatively higher orrelatively lower speeds of the generators G and G2, which rotate withthe motors M and M2 respectively.

Consequently, by shifting the contactor 83, the speed of both motors maybe increased or decreased or even reversed, but the speed ratio betweenthe two motors will remain unchanged. Also, if the direction of rotationof one motor is reversed by adjustment of controller C3, the directionof rotation of the other motor will be simultaneously reversed.

The small generators G and G2, being of the brush-commutator type withpermanent magnet field systems, are particularly adapted for use in mycontrol apparatus, as the voltage is directly proportional to thearmature speed and is reversed if the direction of armature rotation isreversed. Thus a vvoltage proportioned to the speed of M' or M2 isalways generated of such polarity as to oppose and nally neutralize thevoltage on the associated coil 60 or 14.

I have thus provided very simple mechanism for separately controllingeach of two motors, both as to speed and direction of rotation, and Ihave also provided a simple master controller by which both motors maybe simultaneously adjusted as to speed and direction without change inthe established speed ratio.

While I have shown my invention as controlling two motors only, it willbe obvious that additional resistances may be introduced into theexternal circuit for the control of additional motor units.

Having thus described my invention andI the advantages thereof, I do notwish to be limited to the details herein disclosed, otherwise than asset forth in the claims, but what I claim is:

1. In a means to control the speeds of a plurality of motors, thatimprovement which comprises a resistance unit having a variableresistance in parallel with two xed resistances in series, an externalcontrol circuit connected to the common terminals of said parallelresistance circuits, and a current supply connected to the junction ofsaid fixed resistances and to a shiftable contactor for said variableresistance.

2. In a means to control the speeds of a plurality of motors, thatimprovement which comprises a resistance unit having a variableresistance in parallel with two iixed resistances in series, an externalcontrol circuit connected to the common terminals of said parallelresistance circuits, and a current supply connected to the junction ofsaid fixed resistances and to a shiftable contactor for said variableresistance, said fixed resistances being equal in resistance value.

3. In a means to control the speeds of a plurality of motors, thatimprovement which comprises a resistance unit having a variableresistance in parallel with Itwo fixed resistances in series, anexternal control circuit connected to the common terminals of saidparallel resistance circuits, and a current supply connected to thejunction of said fixed resistances and to a shiftable contactor for saidvariable resistance, said xed resistances being equal in resistancevalue, and said external circuit having control devices therein for aplurality of motor units.

4. The combination in a speed control means as set forth in claim 3, inwhich the external circuit also has a pair of equal resistances for eachcontrolled motor unit, all of said resistances being in series in saidexternal circuit, and in which each motor unit has a separate speedcontrol circuit including a source of current supply, one end of saidseparate circuit being connected to the junction between the twoassociated equal resistances for said unit and the other end of saidcircuit being connected to a contactor shiftable to any point on eitherof said equal resistances, whereby the speed and direction of rotationof each motor unit may be separately adjusted by movement of itsshiftable contactor and whereby the speeds of all of said motor unitsmay be simultaneously and proportionately varied by moving thefirst-mentioned contactor along its variable resistance.

5. A speed control unit comprising two equal fixed resistances inseries, a third resistance connected in parallel with said two fixedresistances, an external control circuit connected to the commonterminals of said parallel resistance circuits, a contacter shiftablealong said third resistance and connected to a source of current supply,and a connection from said source of supply to the junction between saidtwo fixed resistances.

SAMUEL T. WEBSTER.

